Typically, a solenoid valve comprises an armature movable between a first and second position. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a coil of wire and moved in the opposite direction by a return spring. When the armature impacts a stop, it bounces. Each bounce of the armature, or valving element, meters a small uncontrolled amount of fuel into the engine, to the detriment of emissions. As can be appreciated, the leakage of fuel into the engine will result in very unfavorable fuel economy. Furthermore, the bounce of the armature affects the operation of a fuel injector by prolonging or shortening the duration of injection, causing excessive wear in the valve seat area.
The armature is typically a solid structure with "fuel holes" that allow fuel to pass through to the valve and orifice. The energy from the impact of the armature against the pole piece causes resonances in the parts and assemblies of the injector, such as the housing, housing-inlet connector, connector, and armature needle.
Certain fuel-injected automobile engines operate sufficiently quietly that certain audible noise from the operating fuel injectors may be distinguished by some persons in the vicinity. The detection of such noise may be deemed objectionable by the manufacturer, and/or it may be mistakenly perceived by the customer as a defect in the product, despite the fact that it is operating properly.
It is seen then that it would be desirable to have operating fuel injectors which achieve a meaningful noise reduction in an effective manner, without requiring major revisions to component parts of existing fuel injectors.